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DECADE II user manual

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1. Antec Industrieweg 12 2382 NV Zoeterwoude The Netherlands Electrochemical Detector User manual 171 0011 Edition 12 2015 oh ISO T 31715813333 F 31715813334 info myantec com www myantec com M certified Copyright 2015 Antec The Netherlands Contents of this publication may not be reproduced in any form or by any means including electronic storage and retrieval or translation into a foreign language without prior agreement and written consent from the copyright of the owner The information contained in this document is subject to change without notice ROXY ALEXYS DECADE DECADE II INTRO Flexcell ReactorCell SenCell VT 03 u PrepCell SynthesisCell ISAAC HyREF are trademarks of Antec Whatman word and device and Whatrnan word only are trademarks of Whatman International Ltd SOLVENT IFD and AQUEOUS IFD are trademarks of Arbor Technologies Inc Clarity DataApex are trademarks of DataApex Ltd Microsoft and Windows are trademarks of Microsoft Corporation Excel is a registered trademark of the Microsoft Corporation The software and the information provided herein is believed to be reliable Antec shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing performance or use of software or this manual All use of the software shall be entirely at the user s own risk Chapter 1 DECADE Il electrochemical detector 3
2. Decreasing the integrator frequency to less than half the pulse frequency changes the peak shape Fig 33E When the peak width is too small there are two options either less data points are collected for such a peak or the pulse and integrator frequency are both increased In the latter case the pulse duration is decreased which will change other detection parameters as well In practise the pulse frequency almost never interferes with the HPLC analysis Working electrode material Gold and platinum are used as working electrodes for PAD Glassy carbon appears to be unsuitable due to the high electric capacitance of this material Furthermore resurfacing of the noble metal working electrode is based upon formation and removal of a metal oxide layer This is impossible with glassy carbon The change in cell current during the pulse mode is illustrated in Fig 34 When the potential is changed a large charging current is detected Fig 34 peak 1 3 and 5 followed by a stabilisation of the current Fig 34 part 2 4 and 6 The output signal is sampled during a fraction of part 2 depending on the pulse settings The response of the glassy carbon material is considerably different from the noble metals The capacitance of the electrode material is very high such that the charging current is not stabilised before start of the next potential step This pattern makes detection impossible Examples of carbohydrate analyses are given in
3. Injector sensor Oven Diagnostics Service mode Config mode Firmware Environmental Second flow cell DC mode Ranges Filter cut off Noise 110 240 VAC 50 60 Hz 260 VA autosensing DC PAD and Scan between 2 00 and 2 00 V in 10 mV increments or 2 50 and 2 50 V in 10 mV increments DECADE II MD p n 171 0035MD and 171 0038MD between 1 and 1 V or between 10 and 10 V 20 bit D A converter between 50 and 50 of max output voltage 5 steps pulse of 10 of max output triggered by keyboard rear panel TTL input or RS232C control Full parametric instrument control data acquisition at 1 2 5 and 10 Hz Starts system clock at injection height 37 cm from 7 C above ambient to 45 C accuracy 0 5 C stability 0 1 C accommodates column and flow cell s LCD screen keyboard and noise internal dummy cell system settings amp calibration parameters menu for system customisation and optimisation upgradeable via PC RS232 operating temperature 4 40 deg C rel humidity 20 to 80 non condensing Acquisition and control of second flow cell option 10 pA 200 uA in 1 2 5 steps 0 5 0 01 Hz in 1 2 5 steps better than 2 pA with a dummy cell load of 300 MQ and 0 5 uF with filter off Ec 800mV and temperature of 30 C 74 DECADE II user manual ed 11 PULSE mode Range 10 nA 200 pA in 1 2 5 steps Filter cut off 0 5 0 01 Hz in 1 2 5 steps Pulse times t1 100 2
4. Range off 15 450C selectable in 10C steps The oven is stable from 5 C above ambient ts pulse setup2 Controls the duration of the sampling C time in the pulse mode The time can be set between 20 and 100 ms in 20 ms increments Tsensor system Displays active temperature sensor S Valve prog Controls the electrically actuated C injector during execution of a time file Forces this valve to load LD or inject INI Valve config User confirmation whether a manual S valve is connected to phone jack C on rear panel If present INJ I or INJ L appears in DC Pulse Status screen Vout stat dc Displays output signal S pulse scan events setup run noise Vout config Controls max output signal 1 or 10V C full scale for all sensor boards 30 DECADE II user manual ed 11 ALEXYS DECADE II driver Full control and data acquisition is supported in ALEXYS data system Important difference with stand alone operation is that timed events are not executed from time files but from the events page in ALEXYS software DECADE Il time files are not supported in ALEXYS data system Use events page instead IN DECADE II LC EC workstation System1 ALEXYS1 smt l x General Sensor 1 Channels Links Common pc mode Program Configuration Gel on On Method data Actual DC x Mode DC 10 Data acquisition rate Hz 10 Conk Ci Data point nA z COMP switch
5. obtained if the cell is switched ON with only water or another non conducting mobile phase Also be sure that no air bubbles are trapped in the flow cell The outlet tubing from the flow cell should lead to a reservoir that is at a higher level than the flow cell This ensures a minute back pressure which prevents air bubble entrapment The outlet tubing should be under the liquid level to avoid electrical noise induced by dripping of mobile phase Set the cell potential see page 63 for optimisation of the potential switch ON the flow cell see page 19 and allow the system to stabilise for approximately 30 min A good stabilisation curve shows a mono exponential decline without jumps and or spikes Connect the data system to the output see page 30 Your system is now ready for use CHAPTER 2 Installation guide 17 The DECADE II has been developed for continuous operation For maximum stability it is advised to leave the system ON continuously If preferred the flow cell may be switched OFF at night Maintenance Perform periodic leak checks on LC tubing and connections and check if the drain on the bottom of the oven compartment is not blocked or closed Do not allow flammable and or toxic solvents to accumulate Follow a regulated approved waste disposal program Empty and clean waste container regularly Never dispose of such products through the municipal sewage system This instrument has a lithium ba
6. Type S is status F is function and C is control Parameter screen Description Type 28 gt 300C _ dc stat Displays the actual left value and the S pulse stat pre set oven temperature right value scan stat run ADD prog Adds the active data line to the time file F Confirmation is asked for if an existing time is overwritten As time 0 00 always exists changing this time results in an overwrite warning see page 39 EVENTS dc setup Enters EVENTS EVENTS SETUP F pulse setup2 screen for editing and running a time file AZERO dc stat run Sets the output voltage to 0 V or to the F pulse stat offset voltage see page 30 Control scan stat Comp off changes to Comp on If cell current exceeds the max compensation a message cell current exceeds max compensation appears In that case max compensation will be applied which may not be the 0 Volt level but higher Azero prog Controls auto zero which can be programmed in a time file See page 39 Toggles between set and not Boot system Displays boot firmware version S CELL ON dc stat Toggles between cell ON and OFF F OFF pulse stat Confirmation is required Switch cell on scan setup off Switching on resets the clock to scan stat 0 00 Pulse mode pulsation occurs as long as the cell is on irrespective which screen is selected Scan mode potential E1 is applied Checks
7. and 50 pulse setup1 pulse stat scan setup scan stat Offs run Displays percentage offset during S execution of a time file Outp prog Control of four output functions in C EVENTS Is open high if 0 is closed low if 1 AUX1 0001 AUX2 0010 relay 1 0100 relay 2 1000 Combinations are possible POLAR dc setup Inverts output polarity toggle between F pulse setup2 and Requires confirmation PREV several Return to previous screen F screens QUIT run Aborts the time file and returns to the F EVENTS SETUP screen The cycle counter Cy is reset to 1 Outputs Aux 1 and 2 and Relays 1 and 2 are reset status 0000 Range dc setup dc Range setting varying from 10 pA to C stat prog 200 HA full scale in 1 2 and 5 steps pulse In the pulse and scan mode 10 nA to setup 200 uA full scale can be used pulse stat scan setup 28 DECADE II user manual ed 11 Parameter screen Description Type scan stat RUN events setup Enters RUN screen System waits F waiting for the START input trigger external or keyboard to start a run S scan setup Scan speed can be set from 1 50 C mV s in 1 2 5 steps SCROLL prog Scrolls through a time file F SPD scan stat Scan speed can be set from 1 50 C mV s in 1 2 5 steps START run scan In DC and pulse mode toggle between F st
8. at sensitive ranges and maximum compensation at the less sensitive ranges This is an inevitable consequence of the tremendous dynamic range that is covered by electrochemical detection Table II DC ranges and maximum compensation Range FS Max comp Range FS Max comp 200 A 2 5mA 20 nA 2 5 pA 100 UA 2 5mA 10 nA 2 5 pA 50 HA 2 5 mA 5 nA 250 nA 20 uA 2 5 mA 2 nA 250 nA 10 uA 2 5 mA 1nA 250 25 nA 5 HA 2 5mA 500 pA 250 25 nA 2 HA 25 uA 200 pA 250 25 nA 1 pA 25 uA 100 pA 25 nA 500 nA 25uA 50 pA 25 nA 200 nA 25uA 20 pA 25 nA 100 nA 25yA 10 pA 25 nA 50nA 2 5HA From firmware gt 3 00 the noise level in ranges 200 500 pA and 1 nA has been improved considerably by selecting a different amplifier setting As a consequence max compensation is changed to 25 nA for these ranges In the PULSE and SCAN mode current is much higher than in DC mode Therefore it is not possible to select pA ranges Table III PAD ranges and maximum compensation Range FS Max comp Range FS Max comp 200 A 2 5mA 500 nA 25uA 100 UA 2 5 mA 200 nA 25 HA 50 pA 2 5 mA 100 nA 25 HA 20 A 2 5 mA 50 nA 2 5 pA 10 pA 2 5 mA 20 nA 2 5 pA 5 HA 2 5 mA 10 nA 2 5 pA 2 UA 25 pA 1 HA 25 pA Offset 38 VO ALX A HOA DECADE II user manual ed 11 A maximum offset of 50 and 50 in 5 steps can be set For example 20 is a 200 mV offset when the maximum output is 1 0 Volt 2 V at max 10 0 V Polarity The polarity of the output can be in
9. gt gt CHAPTER 2 Installation guide 15 DI Fig 3 Installation of the DECADE II 4 Prior to connection of the HPLC system to the detector all metal parts should preferably be passivated with 15 nitric acid during 20 A min Make sure that all parts that are not acid resistant such as nylon inlet filters column and flow cell are not connected during this step The acid is flushed through the pump the pump tubing the dampener the injector in load and inject position and to waste 5 After flushing with nitric acid the system must be thoroughly flushed with demi water Make sure that no traces of nitric acid are left in the tubing or pulse dampener check with pH paper Flush the system with HPLC buffer If an ISAAC reference electrode is used make sure that the buffer contains 2 mmole I chloride KCI or NaCl ions 6 Before connecting a new column read the manufacturer s instructions Our experience is that thorough pre conditioning of a column is always required Only a pre conditioned column is electrochemically clean If not the background current may be unacceptably high and substantial fouling of the working electrode occurs For reversed phase columns flushing with 50 methanol in water for 3 days at a low flow rate is highly recommended Before switching to mobile phase flushing with water 10 column volumes is recommended to prevent precipitation of buffer salts 16 DECADE II user manual ed 11 7 Pa
10. the DC mode Scanning takes place on top of the broad peak between 0 5 and 2 5 min after injection in FIA mode 5 The sampling frequency of the integrator is set at 1 Hz This is the same frequency as the voltage steps during the scan If a higher sampling frequency is chosen a typical stepwise pattern may appear 6 Inthe SCAN SETUP screen an upper and a lower potential is chosen The cycle is set at half The range is set at 5 uA A scan speed of 10 mV s is selected 7 The analyte is injected and the scan is started by pressing the START in the SCAN STAT screen of the DECADE II at the time the analyte plug enters the flow cell see 4 8 A background scan is obtained by scanning the HPLC buffer For reliable results it is recommended to repeat each scan three times Using scan mode in ALEXYS data system The ALEXYS data system offers a convenient interface to construct a scanning voltammogram Open the DECADE II device driver and click on Scan Shell This opens the actual scan window and half or full scans can be acquired Continuous scanning is done by recording multiple full scans after each other CHAPTER 8 Optimisation of working potential 71 Mali sis t ve J 72 DECADE II user manual ed 11 CHAPTER9 Specifications DECADE II 73 CHAPTER 9 Specifications DECADE Il General specifications Power Operating modes Potential range Output Offset Event marker Auto zero RS232C
11. 0 um spacer REF Hy REF I cell ca 435 nA References 1 D C Johnson D Dobberpuhl R Roberts and P Vandeberg Review Pulsed amperometric detection of carbohydrates amines and sulphur species in ion chromatography the current state of research J Chromatogr 640 1993 79 96 2 D C Johnson en W R LaCourse LC with pulsed ECD at gold and platinum electrodes Anal Chem 62 1990 589A 597A 3 W R LaCourse en D C Johnson Optimization of waveforms for pulsed amperometric detection of carbohydrates following separation by LC Carbohydrate Research 215 1991 159 178 4 W R LaCourse en D C Johnson Optimization of waveforms for pulsed amperometric detection of carbohydrates based on pulsed voltammetry Anal Chem 65 1993 50 55 CHAPTER 8 Optimisation of working potential 63 CHAPTER 8 Optimisation of working potential Introduction A current voltage I E relationship or voltammogram characterises an analyte It gives information on the optimum working potential which can be used to improve detection sensitivity and selectivity There are several ways to obtain a voltammogram A hydrodynamic voltammogram is obtained in the DC mode by running several chromatograms at different working potentials Both peak height and background current are plotted against the working potential A scanning voltammogram is obtained in the so called scan mode of the DECADE II the voltage runs between two pre set values and the curren
12. 000 ms t2 0 2000 ms t3 0 2000 ms in 10 ms steps Sample times 20 ms t1 60 ms with 20 ms increments SCAN mode Range 10 nA 200 pA in 1 2 5 steps Scan rate 1 50 mV s in 1 2 5 steps Cycle half full or continuous Events DC mode 5 files and pulse mode 4 files end cycle time number of cycles and oven temperature Time based control of 50 time points as to range filter output contacts 2 TTL 2 relays auto zero offset valve position if present and E cell Rear panel I O connections Mains Output 2 Connectors 15 pins A B manual valve C RS232C connector Physical specifications Dimensions 44 D x 22 W x 44 H cm 17 3 D x 8 7 W x 17 3 H Weight 14 kg without flow cell and column Flow cells Confined wall jet design working volume determined by spacer thickness and WE diameter Spacers 25 50 or 120 um stackable WE diameters 0 7 3 mm 2 mm standard Cell volume 11 nl minimum WE electrodes Glassy carbon gold platinum silver and copper Reference electrodes salt bridge Ag AgCl in situ Ag AgCl ISAAC HyREF Auxiliary electrode stainless steel Wetted materials PCTFE FEP 316 SS Viton Silver Silver chloride and WE Max pressure 40 psi 2 8 bar CHAPTER 10 Error messages 75 CHAPTER 10 Error messages Table X Error messages Error 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Message Incompatible boot version Control board e
13. 20 80 non condensing Place the detector on a flat and smooth surface Do not block the fan located at the bottom of the detector Fig 2 Blocking the fan will impair the cooling capability of the power supply Fan Fig 2 Location of power supply fan DECADE II Inspect the detector for possible damage and make sure that all marked and ordered items on the checklist are included Switch ON the DECADE II by the mains switch on the rear panel Ensure that the power on off switch and power cord are always accessible HPLC connections Use proper eye and skin protection when working with solvents The manufacturer will not accept any liability for damage direct or indirect caused by connecting this instrument to devices that do not meet the relevant safety standards The pump connected to the system should be specifically designed for use in High Performance Liquid Chromatography and capable of delivering flow rates typically in the range between 1 L min up to 10 mL min Please carefully follow the next steps for a successful installation and start up 1 The installation of the flow cell and column is shown in Fig 3 2 If a manual injector is applied with position sensor the sensor cable must be connected to C on the rear panel to enable INJECT LOAD functions 3 If an electrically actuated valve is mounted connect the digital input output cable to B on the rear panel to enable INJECT LOAD functions
14. 240000 140000 40000 Fig 20 Frequency tells how often something happens 1 peak in about 0 25 min 15 s f 1 15 0 07 Hz CHAPTER5 Noise suppression ADF 41 This is further illustrated by an overlay of the same chromatographic peak with a sine of 0 07 Hz Fig 21 540000 440000 340000 240000 140000 40000 3 0 3 2 3 4 3 6 3 8 4 0 42 44 46 48 5 0 Fig 21 Overlay of a chromatographic peak with 0 07 Hz sine Typically in chromatography narrow peaks are in front of a chromatogram while peaks with longer retention times get wider As a consequence frequencies are not constant but vary between 0 1 0 01 Hz which corresponds to 10 100 s peak width 698000 ADF 598000 10s lt s 4 0 10 Hz 0 025 Hz 498000 398000 lt 298000 198000 98000 2000 Fig 22 Typical chromatogram with peak widths between 10 100 s Noise in chromatography can come from different sources Pump pulsations are typically shown as a very regular noise pattern while electronic noise has amore random character This is illustrated in Fig 23 where a noise trace is shown with an overlay of a 10 and 0 4 Hz sine 42 DECADE II user manual ed 11 sine f 10 Hz 10 sine f 0 4 Hz 30 31 32 33 34 35 36 37 38 39 40 Fig 23 Typical random noise in chromatography low
15. 69 X 1 0 060606061 X 3 0 255411255 X 5 X 7 X 9 0 233766234 0 233766234 0 060606061 0 168831169 0 090909091 Note that the sum of coefficients is exactly 1 Y n is the output data point X n are input data points Generally spoken the performance of a digital filter CHAPTER 5 Noise suppression ADF 45 improves with more input data points but also more processor capacity is required for the large number of calculations Applying ADF in chromatography If noise frequencies in LC EC differ from the frequency of the signal noise can be suppressed Using the right filter setting cut off frequency will specifically attenuate noise and improve the signal to noise S N ratio No matter how advanced a filter is it is only possible to apply low pass filtering if noise frequencies are higher than the frequency of the signal 400000 300000 200000 100000 400000 300000 200000 100000 0 400000 300000 200000 100000 0 0 Fig 27 From top to bottom filter setting of 0 5 0 02 and 0 002 Hz Narrow peaks in front of the chromatogram are deformed at 0 005 Hz whereas wider peaks show hardly any deformation see peak at t 13 min Attenuation of noise is shown in the close up on the right 46 DECADE II user manual ed 11 Prerequisite for a good noise filter for d
16. Blocking the fan will impair the cooling capability of the power supply General precautions Do not close or block the drain Do not allow flammable and or toxic solvents to accumulate Follow a regulated approved waste disposal program Never dispose of such products through the municipal sewage system This instrument has a lithium battery inside Replacement of the battery should be performed by qualified service personnel Dispose the battery according to chemical waste only f Perform periodic leak checks on LC tubing and connections LC equipments should be used by trained laboratory personnel only Use proper eye and skin protection when working with solvents Additional safety requirements or protection may be necessary depending on the chemicals used in combination with this equipment Make sure that you understand the hazards associated with the chemicals used and take appropriate measures with regards to safety and protection Use of this product outside the scope of this guide may present a hazard and can lead to personal injury Spare parts and service availability Manufacturer provides operational spare parts of the instrument and current accessories for a period of five years after shipment of the final production run of the instrument Spare parts will be available after this five years period on an as available basis Manufacturer provides a variety of services to support her customers after warranty expirat
17. Declaration of conformity We Antec Leyden B V Zoeterwoude The Netherlands declare that the product DECADE II Electrochemical Detector type 171 to which this declaration relates is in conformity with the following directives Safety 2006 42 EC Safety requirements for laboratory equipment 1EC61010 1 2001 2 ed Class I Installation cat Il Pollution degree 2 Particular requirements for laboratory IEC61010 2 010 2003 2 ed equipment for the heating of materials Immunity 2004 108 EC Electromagnetic immunity EN61326 1 2006 EN61000 4 2 EN61000 4 3 ENV50204 EN61000 4 4 EN61000 4 5 EN61000 4 6 EN61000 4 8 EN61000 4 1 1 Emissions 2004 108 EC Electromagnetic emission EN61326 1 2006 EN55011 Class B EN61000 3 2 EN61000 3 3 Attention Only use manufacturer supplied cable s to connect with other devices Part numbers 250 0122 RS232 cable 250 0130 I O cable and 250 0128 output cable Thoroughly connect shielding to common Manufacturer will not accept any liability for damage direct or indirect caused by connecting this instrument to devices which do not meet relevant safety standards June 25 2015 4 DECADE II user manual ed 11 Intended use For research purposes only While clinical applications may be shown this instrument is not tested by the manufacturer to comply with the In Vitro Diagnostics Directive WEEE directive All equipment of Antec Leyden which are subjected to the WEEE
18. E2 E3 pulse setup2 Controls the cell potential settings of C the pulse Ec prog dc Controls the cell potential is 10 mV Cc only events steps between 2 00 and 2 00 V or setup dc 2 50 and 2 50V for the DECADE II only dc MD Can only be set or changed after setup confirmation with the enter button Controls the cell potential in a time file without confirmation Ec run dc only Reflects the set cell potential Displays S scan stat the actual cell potential in the scan during mode 26 DECADE Il user manual ed 11 Parameter screen Description Type scanning EndCycle prog Enters a screen to set EndCycleTime F Controls duration of a time file max 999 99 min When this time is reached the execution of the time file stops If programmed the next run is started Cannot be smaller than smallest time in time file 0 01 min Is therefore never smaller than 0 01 min Events dc setup Enter events menu F pulse setupup2 File events setup Selected time file number In the DC C mode file numbers 1 5 are available in the pulse mode file numbers 6 9 can be selected The time files remain stored in RAM also after switching off the DECADE Il Time files can be uploaded via RS232 Filt dc setup dc Filter settings 0 5 to 0 001 Hz cut off C stat prog frequency in 1 2 5 steps Filt run Reflects the actual filter setting S Fi
19. ECADE II user manual ed 11 Safety practices The following safety practices are intended to insure safe operation of the equipment Electrical hazards The removal of protective panels on the instrument can result in exposure to potentially dangerous voltages Therefore disconnect the instrument from all power sources before disassembly Untrained personnel should not open the instrument WARNING RISK OF ELECTRIC SHOCK DISCONNECT POWER BEFORE SERVICING AVERTISSEMENT RISQUE DE CHOC ELECTRIQUE COUPER L ALIMENTATION AVANT LA MAINTENANCE Replace blown fuses with fuses of proper type and rating as stipulated on the rear panel and specified in the installation section of this manual The fuse holder is integrated in the mains connector Ensure that the instrument is never put in operation with fuses of a different type This could cause fire V 100 240 V_ FUSE RATING WARNING RISK OF FIRE REPLACE FUSE AS MARKED AVERTISSEMENT RISQUE DE FEU 2 SAT 250V REMPLACEZ LE FUSIBLE COMME INDIQU Connect the detector to a grounded AC power source line voltage 100 240 VAC The instrument should be connected to a protective earth via a ground Chapter 1 DECADE Il electrochemical detector 7 socket The power source should exhibit minimal power transients and fluctuations Replace faulty or frayed power cords Place the detector on a flat and smooth surface Do not block the fan located at the bottom of the detector
20. Fig 30 Typical PAD pulse settings are given in Table VII and Table VIII these settings may be used as starting point for further optimisation Carbohydrates are oxidised at a pH of 12 or higher which puts specific demands on the HPLC system used see above Table VII Potential settings for PAD of carbohydrates at a gold working electrode s 1 2 3 t ms 100 400 200 200 E mV 150 750 800 Table VIII Potential settings for PAD of glycols alcohols aldehydes at a platinum working electrode s 1 2 3 t ms 20 300 100 100 E mV 200 1300 100 CHAPTER 7 Pulsed amperometric detection 61 1 3 I p2 4 IN se ae 6 o J h J i L Au i K i N i SA RO la Re in ai kine Ne ko Viti L GC Fig 34 Change in cell current during PAD The cell current of the noble metals gold Au and platinum Pt is stabilised faster than the cell current of glassy carbon GC due to a much lower capacitance of the noble metals For Pt and GC the negative peaks run far off scale however the profile is similar to the mirror image of the positive peaks 62 DECADE Il user manual ed 11 Table IX LC EC conditions for PAD of carbohydrates detector DECADE II flow rate 1 0 ml min mobile phase 200 mM NaOH sample disaccharides 100 nmol l 20 ul injection temperature 30 C flow cell VT 03 flow cell with 3 0 mm gold working electrode mounted with 5
21. ale Fig 11 DECADE II signal processing from electrochemical flow cell to output The signal from the I E converter can be compensated with auto zero or offset and is digitised using a 24 bits ADC In the CPU the signal is processed for example noise filtering or more complex data processing in PAD Finally after the 20 bits DAC the signal is set to a 1 or 10 V full scale analogue output Dual flow cell control The DECADE Il electronics are located on 2 different PCB s printed circuit boards The control board and the sensor board The control board is dedicated to communication with PC RS232 and keyboard amp display It has a processor with a so called event handler that takes care of all user 34 DECADE II user manual ed 11 commands and hardware interrupts The sensor board is fully dedicated to data acquisition and flow cell control By using this architecture it is possible to extend the functionality of the DECADE II to more than one flow cell by simply adding a sensor board The control board and other hardware is prepared for more than one sensor board Typically a two flow cell configuration can be used in serial or parallel mode detection Serial mode detection In serial mode one LC system is used with 2 flow cells in series For data acquisition 2 data channels are applied with the same time base Serial mode detection is especially suitable for OX RED or RED OX applications examp
22. aphic conditions reliable information about the S N ratio is obtained In case of metal working electrodes it is also advisable to use a hydrodynamic voltammogram On the metal working electrode an oxide layer is formed which affects the electrochemical reaction and makes the interpretation of a scanning voltammogram difficult 10 nA A E V Fig 36 Hydrodynamic voltammogram of norepinephrine A at a glassy carbon working electrode and the current of the baseline B At E the electrochemical signal becomes diffusion limited An alternative for the chromatographic construction of an I E relationship is the application of scanning voltammetry The working potential runs between two pre set values and the current is measured while the analyte is continuously flushed through the flow cell As peak heights are used the signal in Fig 36 line A is only due to the analyte The signal in Fig 37 line A is the sum of the analyte signal and the background signal Subtracting both lines in Fig 37 results in a similar I E relationship as in Fig 36 line A It takes only a few minutes to construct a scanning voltammogram This is an advantage especially when a number of analytes have to be characterised However as the scan is obtained in flow injection analysis FIA without analytical column it is a prerequisite to have the pure analyte dissolved in buffer Any contamination may lead to N artifacts A blank scan of the buffer shoul
23. at STOP and START execution of a time file Starts a scan in scan mode STOP run scan Scan mode STOP aborts scan and F stat resets cell potential to E1 DC and pulse mode toggle between STOP and START to control execution of a time file Pressing STOP aborts this run cycle counter Cy is reset to 1 STOP also deactivates the outputs Aux 1 and 2 and Relays 1 and 2 status 0000 and sets the electric valve to load if present t pulse Displays the total duration of one pulse S setup2 t1 t2 t8 pulse stat t1 t2 t3 pulse setup2 Duration of potential step E1 E2 or C E3 Time can be set between 0 t2 t3 or 100 t1 and 2000 ms in 10 ms increments Temp config Controls the temperature of the oven C Range off 15 450C selectable in 10C steps The oven is stable from 5 NC above ambient oven temperature Temp events setup Controls the temperature of the oven C is stored with time file Temperature of active time file temperature overrules other temperature setting after selecting START Time prog Controls the time to execute a data line C in atime file can be set with 0 01 min resolution Maximum time is 999 99 min The time to stop the execution of CHAPTER 3 DECADE II controller 29 Parameter screen Description Type a time file must be programmed by EndCycleTime Toven dc setup Controls the temperature of the oven C pulse setup1
24. ata acquisition in liquid chromatography is that it improves the S N ratio without significant distortion of the signal of interest This is particularly difficult if the frequency of the signal is close to the frequency of the noise The DECADE II has a number of filter settings to optimise for best possible signal to noise ratio The width of the peaks of interest is important because wider peaks allow stronger filter settings simply because of the lower frequency of such peaks Advised filter setting to start further optimisation is given as Filter setting 1 2 peak width So at a 10 s peak width a 0 05 Hz filter setting is advised If peaks are 50s a 0 01 Hz filter is advised to start with Note that if a chromatogram has interesting peaks of 10 s as well as 50 s it may not be possible to work with one filter setting In that case it is advisable to switch to a stronger filter setting for the second half of the chromatogram using a timed event To optimise for the best S N ratio use the lowest acceptable cut off frequency After optimisation do not change the cut off frequency setting during analysis of a calibration sequence Use the same settings for analysis of samples and calibration standards ADF off ADF 0 02 amp 0 001 Hz programmed Blank ADF on a SONATA 0 02 Hz 0 001Hz Te ee a 5 10 15 20 25 Fig 28 Analysis of 20 pmole L 5 hydroxytryptophan 5 HIAA and 5HT using ADF for improving detect
25. ctivity and reproducibility In the example of Fig 36 a working potential E1 of 0 8 V is chosen Optimisation using a voltammogram Sometimes when interfering peaks appear in the chromatogram it is possible to optimise the method with regard to selectivity If the interfering compound has a higher oxidation potential a working potential is chosen that gives the best selectivity i e the largest difference in peak height In the example of Fig 38 the selectivity for compound X is improved considerably by decreasing the potential to E2 or E1 Obviously if compound Y is the 66 DECADE II user manual ed 11 compound of interest optimisation of selectivity in this way is not possible and the chromatography has to be optimised Electrochemical detection differs from most other LC detection methods in that a reaction takes place in the detection cell Due to reaction kinetics an increased temperature speeds up the oxidation reduction reaction However this not only holds for the analyte but also for the background current and possible interferences An elevated temperature will therefore not automatically lead to a better detection A constant temperature is of paramount importance for a stable baseline and reproducible detection conditions 4 E E E E Fig 38 Selectivity in LC EC of compound X and Y is optimised by choosing the working potential with the largest difference in peak height Electrochemical reactions are pH
26. d be used to distinguish between solvent peaks and analyte peaks CHAPTER8 Optimisation of working potential 65 As can be seen in both Fig 36 and Fig 37 when the working potential is increased the electrochemical reaction is enhanced hence the signal increases At a certain potential the I E curve flattens All analyte molecules that reach the working electrode are converted at such a high rate that the analyte supply becomes the limiting factor At the working electrode surface a stagnant double layer exists where molecular transport takes place by diffusion only Therefore the current at and beyond this potential is called the diffusion limited current J f F T o af A ses a pera wer 7A r va ji B a RI ae F rs per eterea srt 0 0 3 06 0 9 1 2 EV Fig 37 Scanning voltammetry of 1 0 umol norepinephrine A at a glassy carbon working electrode at a scan speed of 10 mV s Scan B is the blank solvent With respect to sensitivity a high working potential is important However at higher working potentials more analytes are detectable So as to selectivity a low working potential will be favourable Working at a potential on the slope of the I E curve will result in less reproducibility Not only a small fluctuation in the applied potential but any change in the system may result in a large difference in current In practice the choice of the working potential is a compromise between sensitivity sele
27. de the reverse scan i e from 0 2 V to 1 2 V and back to 0 2 V In the continuous mode the voltage is swept up and down between both potentials CHAPTER 8 Optimisation of working potential 69 0 2 Fig 42 1 DMP 2 P 3 CP 4 NP 5 blank 0 5 0 8 1 1 1 4 E M The scanning voltammograms of 2 4 dimethylphenol DMP phenol P 2 chlorophenol 2 CP and 4 nitrophenol NP The following procedure is used to obtain the voltammograms in Fig 37 and Fig 42 1 The column is removed from the LC system The voltammogram is recorded in the flow injection analysis FIA mode The pure compound is dissolved in preferably the HPLC buffer at a concentration of ca 10 100 pmol l When the analyte is already in solution it should be diluted in HPLC buffer until the desired concentration An injection loop of 100 tl is installed and the LC flow rate is set at 40 ul min The analyte plug will than be detected during approximately 2 5 minutes The flow rate is lowered if more scanning time is needed An initial run is started in the DC mode at a high potential to estimate the required start and stop time of the scan after sample injection Fig 43 In the scan mode the scan is obtained at the flat top of an analyte plug The analyte delivery should be constant Fluctuations result in unreliable results 70 DECADE Il user manual ed 11 start a t min Fig 43 Chromatogram of the analyte plug obtained in
28. directive shipped after August 13 2005 are compliant with the WEEE marking requirements Such products are labelled with the crossed out wheelie depicted on the left site Ey The symbol on the product indicates that the product must not be disposed as unsorted municipality waste Collection amp recycling information Please ship the instrument back to the manufacturer Antec Leyden the Netherlands at the end of life time of the product The manufacturer will take care of the proper disposal and recycling of the instrument at its facilities Shipping address for the end of life products Antec Leyden Industrieweg 12 2382NV Zoeterwoude The Netherlands In case of questions or if further information is required about the collection amp recycling procedure please contact your local distributor ROHS directive The DECADE Il is ROHS compliant and in conformity with Directive 2002 95 EC Restricted use of Hazardous Substances in electrical and electronic Equipment ROHS Antec Leyden is an ISO 9001 2008 certified company Chapter 1 DECADE Il electrochemical detector Symbols The following symbol are used on the rear panel and oven compartment of the DECADE II A Consult the manual for further safety instructions Frame or chassis ground terminal The following pictograms are used in the DECADE Il manual A Caution Caution risk of electric shock or other electrical hazard high voltage 6 D
29. e TTL output Activated by time file Outp 0001 11 AUX2 Out Free programmable TTL output Activated by time file Outp 0010 12 Cell off In Trigger to switch off cell 13 Start In Starts a time file 14 Auto zero In Auto zero command always accessible when I cell is in display 15 Common Ground Outputs 7 8 12 13 and 14 are level triggered When active output status 9 10 and 11 is low default is high CHAPTER 6 Events and time files Table VI YO contacts connector B No Name YO 1 3 Common 4 Free TTL input In 5 Mark In 6 Status In 7 Status L In 8 11 Common 12 Free TTL output Out 13 Inject marker Out 14 Tol Out 15 ToL Out 53 Function Ground Baseline spike of 10 FS duration 0 1 s Status read of electric valve pos B inject Status read of electric valve pos A load Ground In combination with manual valve connected to connector C high load low inject Forces electric injector to inject Forces electric injector to load Outputs 4 7 12 14 and 15 are level triggered Level triggered TTL input contacts require a minimum TTL low pulse duration of 100 ms If multiple activations are required the next pulse should be given after 100 ms TTL high When the input is kept low only one activation will occur TTL output default high 5 Volt The manufacturer will not accept any liability for damage direct or indirect A caused by connecting this instrument
30. e file used for offset programming at 5 00 min time range filt valve auto output offset E cell id zero 00 00 1 nA 0 5Hz load not 0000 00 0 80 V 00001 00 02 1nA 0 5Hz load set 0000 00 0 80 V 00001 05 00 1nA 0 5Hz load not 0000 30 0 80 V 00001 05 02 1nA 0 5Hz load set 0000 30 0 80 V 00001 14 96 1nA 0 5Hz load not 0000 00 0 80 V 00001 14 98 1nA 0 5Hz load set 0000 00 0 80 V 00001 15 00 EndCycleTime end of run Step by step example In this step by step guide the example from Table IV will be programmed The data acquisition software controls the detector and the autosampler There is no external valve connected to the C or B on the rear panel of the detector For some reason a user wants to give an 30 offset after t 5 00 min 50 DECADE II user manual ed 11 1 Go from MAIN DC SETUP to DC STAT screen to see if the cell is ON or not Set the cell to the desired status and return to DC SETUP From the DC SETUP screen select EVENTS 2 Inthe EVENTS SETUP screen select file number File 1 actual cell potential Ec 0 80 V and the number of cycles Cycles 1 Vout and Ic show the actual cell current and output signal In DC mode file nr 1 5 is available in PULSE mode file 6 9 3 Press PROG to enter the PROG screen Before programming first the contents of file 1 is checked to make sure that the file is not already in use Press SCROLL to see the contents of the file If the file is still releva
31. eplace column Add EDTA to buffer rinse metal parts with 15 HNOs Remedy Refill with saturated KCI add wetted KCI crystals Remove air bubble continuously degas the mobile phase Isolate detector cell set oven temperature Clean WE Tighten connections with care DECADE Il user manual ed 11 Decreased sensitivity low S N ratio Possible cause Fouled WE by dirty samples Cell potential too low Contaminated buffer high Ice Base line oscillations Possible cause Malfunctioning pump regular pattern Over tightened cell bolts Air bubbles in cell or REF Temperature oscillations Contaminated buffer high lcell Fouled WE Fe in buffer Saturation of output Possible cause Damaged REF Damaged WE Cell incorrectly connected Cell potential too high Remedy Clean WE if possible dilute samples Optimise potential Replace buffer do not recycle the buffer Remedy Check pump seals valves Adjust cell bolts check pump pressure Maintenance REF Set oven temperature Replace buffer do not recycle the buffer Clean WE Add EDTA passivate metal parts with HNO3 Remedy Check with spare REF replace if necessary Replace cell block Check connections REF black WE red AUX blue Optimise cell potential CHAPTER 13 Dummy cell 81 CHAPTER 13 Dummy cell External dummy cell A successful dummy cell test confirms that the controller including the cell cable functions properly If the res
32. er applying ADF Frequency A scientific definition of frequency is the number of completed alterations per unit time It has two dimensions count and time Frequency is usually expressed in Hz which is counts per second The counts themselves can run in a regular evenly spaced manner as with sine waves whose curve shapes do not change Alternatively the counts can run in an irregular manner within the specified unit of time If the latter happens frequencies would vary if broken down into t smaller units of time In the example of Fig 18 a signal is shown with a frequency of 12 alterations in 5 minutes To express its frequency in a more scientific way a full period is precisely determined and expressed in Hertz or s It is a sine wave with a frequency of 0 04 Hz Fig 19 40 DECADE II user manual ed 11 400000 UIL VV 300000 S 400000 Fig 18 Example of a signal with regular evenly spaced alterations a sine 400000 300000 200000 100000 0 40 100000 200000 300000 400000 Fig 19 Sine of Fig 18 A full period is 0 41 min 25 s which corresponds to a frequency of 1 25 0 04 Hz Frequency of signal and noise Also a chromatographic peak can be expressed in terms of frequencies The way to determine this frequency is the same The duration of the full peak is measured and expressed in Hz 540000 440000 340000
33. er trace Both frequencies 0 4 and 10 Hz can be recognised amongst others Looking closely to the lower noise trace both frequencies and others can be recognised This is typical for noise in chromatography a collection of more or less random frequencies Low pass noise filters The way noise filters work is by suppressing certain frequencies in the acquired signal Typically low pass filters allow chromatographic peaks low frequency to pass while high er frequency noise is attenuated No matter how advanced it is impossible to use a low pass filter successfully if there is no difference in frequency of signal and noise Analogue filters are made of hardware from capacitors resistors and amplifiers opamps Digital filters are mathematical routines to process an acquired signal Traditionally in many detectors for chromatography an analogue low pass filter is applied rise time filter A passive RC filter consists of resistors and capacitors An active higher order filter can be considered as a number of these RC filters in series In a 4 order filter the signal coming from the first filter is filtered again in a second third and fourth filter During these steps loss of signal occurs simply because of all the resistors that are applied Operational amplifiers which are active components are applied in each stage to restore the signal to its original value With the availability of powerful processors digital sig
34. external equipment During operation a remote screen is shown and the keyboard is locked Keeping the PREV button F1 pressed for 4 seconds disconnects from RS232 control and returns to MAIN 23 45nA 0 50V of f 25 gt 30 C 78 DECADE II user manual ed 11 The manufacturer will not accept any liability for damage direct or indirect caused by connecting this instrument to devices that do not meet the relevant safety standards CHAPTER 12 Troubleshooting guide CHAPTER 12 Troubleshooting guide No detector response Possible cause No power Power switch off Faulty fuse Divergent mains voltage Cell disconnected or switched off Output disconnected Fouled WE High cell current Possible cause Contaminated buffer High WE potential Salt bridge in REF not saturated Retained peaks from previous runs Column is bleeding High amount of Fe in buffer Noisy baseline Possible cause Salt bridge in REF not saturated Air bubble in REF or in cell Slow temperature fluctuations Fouled WE Leaking REF or cell 79 Remedy Check line voltage setting plug in power cord Turn this switch ON at the rear panel Replace fuse Check line voltage see page 13 Check connection Check connection Clean WE Remedy Replace buffer do not recycle the buffer Optimise potential if possible use smaller WE diameter Refill with wetted KCI crystals Wait for elution of these very broad peaks R
35. frequency a typical stepwise pattern may appear in the chromatogram This is normal and only visible after considerable magnification of the chromatogram The background or cell current is usually considerably higher 100 1000 nA than in the DC mode Therefore only nano and microampere ranges are available in the pulse mode After prolonged use of the flow cell with a gold working electrode WE in the pulse mode the gold oxide which is generated at the WE precipitates on the auxiliary electrode AUX This gold oxide coating may electrically isolate the AUX and result in an increase of the noise Cleaning the AUX electrode with metal wool is a way to remove this coating Be careful NOT to touch the working electrode with metal wool Reference electrodes of the Ag AgCl type are less suitable for carbohydrate analysis Due to silveroxide formation they require regular monthly maintenance Hy REF reference electrodes are maintenance free under these conditions and are therefore particularly suited If a mobile phase is used with a high pH pH gt 10 carbohydrate analysis the standard Vespel rotors from the injection valve should be replaced by Tefzel rotors which are pH resistant For carbohydrate analysis only CO2 free sodium hydroxide should be used since carbonate anions may disturb the ion exchange chromatography The CO2 free sodium hydroxide is available from several suppliers as a 50 solution 19 2 mol l NaOH pellets are not reco
36. ged on a time base by user defined commands which enables maximum control to fully automate the detection In addition crucial parameters can be controlled by either relays or TTL 12 DECADE II user manual ed 11 CHAPTER 2 Installation guide 13 CHAPTER 2 Installation guide Unpacking Inspect the transport box for possible damage as it arrives Immediately inform the transport company in case of damage otherwise she may not accept any responsibility Keep the transport box as it is designed for optimum protection during transport and it may be needed again Carefully unpack the system and inspect it for completeness and for possible damage Contact your supplier in case of damage or if not all marked items on the checklist are included Prior to shipment your detector has been thoroughly inspected and tested to meet the highest possible demands The results of all tests are included Installation To unpack the DECADE II lift it from its box by both hands Fig 1 Never lift the DECADE Il at its front door but at its sides lift here Fig 1 Lift instructions DECADE II Install the detector in an area which meets the environmental conditions listed below 14 DECADE II user manual ed 11 Table Environmental conditions Parameter Requirement Storage temperature 40 50 C 104 122 F Storage humidity 0 90 non condensing Operating temperature 4 40 C 39 104 F Operating humidity
37. ion Repair service can be provided on a time and material basis Contact your local supplier for servicing Technical support and training can be provided by qualified chemists on both contractual or as needed basis 8 DECADE II user manual ed 11 Table of contents Declaration of conformity 3 Intended use 4 WEEE directive 4 ROHS directive 4 Symbols 5 Safety practices 6 Spare parts and service availability 7 DECADE II electrochemical detector 11 Installation guide 13 Unpacking 13 Installation 13 Maintenance 17 DECADE II controller 19 Introduction 19 Overview of DECADE II screens 20 Parameters 24 ALEXYS DECADE II driver 30 Detection and parameters 33 Introduction 33 Internal organisation 33 Dual flow cell control 33 Serial mode detection 34 Parallel mode detection 34 Navigation in dual cell menu 35 Parameters 36 Range 36 Offset 37 Polarity 38 Filter 38 Noise suppression ADF 39 Introduction 39 Frequency 39 Frequency of signal and noise 40 Chapter 1 DECADE Il electrochemical detector Low pass noise filters 42 Amplitude response plot 43 Applying ADF in chromatography 45 Events and time files 49 Introduction 49 Step by step example 49 Output events 51 Pulsed amperometric detection 55 Introduction 55 Pulse vs DC 56 Pulse settings 57 Optimisation of wave forms 57 Output frequency 59 Peak width and integrator frequency 59 Working electrode material 60 References 62 Optimisation of working
38. ion limits The S N improvement depends on the composition of the frequency spectrum Improvement up to a factor 100 may be obtained compared to an CHAPTER5 Noise suppression ADF 47 unfiltered signal As high frequency noise is suppressed remaining noise components will be in the same frequency range as chromatographic peaks As suppressing noise will always result in some suppression of signal it is advised to switch the DECADE II to the highest acceptable sensitivity 48 DECADE II user manual ed 11 CHAPTER 6 Events and time files 49 CHAPTER 6 Events and time files Introduction Running an Events table time file enables a time based automated and full parametric control of electrochemical detection ECD This is particularly useful when during a run or between runs settings have to be changed such as the sensitivity auto zero or control of external equipment i e trigger to start integration software etc A time file contains a series of data lines maximum of 50 in which the settings of the DECADE II can be changed with 0 01 min 0 6 s time resolution SCROLL ENDCYCLE Fig 29 Programming a time file using the PROG screen The time file is made using the PROG screen Programmable parameters comprise cell potential range auto zero offset filter board id electrically actuated injector if present and the DECADE Il output contacts to control the status of external equipment Table IV A tim
39. isplay Toggle with the and buttons between sensor boards If the board number does not change it means that the second sensor board is not installed or not properly recognized Second a new 36 DECADE II user manual ed 11 status screen is available in dual cell systems which indicates the status of both cells in a single screen However for convenience it is advisable to use PC control from ALEXYS data system when working with 2 flow cells Antec Leyden DEGADE 11 Gs EG workstation DC PU IL SE SCAN 23 45nA 120 6nA CELL ON Fig 15 DECADE II main menu top with active cell indicator in top right corner Multi STAT screen showing cell 1 DC mode and cell 2 PULSE mode Parameters Operational parameters are controlled from the SETUP screens in the DECADE II Parameters are filter cell potential and offset Temperature is set in CONFIG menu CONF I Gl35 5BOV amp Offs 2Hz POLAR Fig 16 Selection of parameters in the DC SETUP screen Temperature is set in CONFIG menu Range Range selection is done in the SETUP or STAT screen in DC PULSE and SCAN mode A number of ranges can be selected the maximum current that can be compensated for using auto zero and offset differs The high sensitivity ranges 10 pA 5 nA have the best noise specifications In fact CHAPTER 4 Detection and parameters 37 there is a trade off between best noise specification
40. les are analysis of vitamin K and nitro tyrosine using micro HPLC The first flow cell is a reactor cell that converts the analyte of interest in a detectable substance The second flow cell is a VT 03 cell which is used for detection Note that it is necessary to work with micro HPLC because the conversion rate of the reactor cell is too small when using standard HPLC ALEXYS system 1 channe 12 ALEXYS syste m1 charnel 1 cell opion ALEXYS 100 d amp a system DE CADEII with dual Fig 12 Typical configuration for serial mode detection Cell 1 is a reactor cell cell 2 is a VT 03 cell for detection Channel 1 and 2 use the same time base of system 1 Parallel mode detection In parallel mode 2 HPLC systems are used with 2 flow cells In fact the DECADE Il is operated as if 2 independent detectors are in one housing CHAPTER 4 Detection and parameters 35 pump 1 necti column 1 ALEXY S syste m1 column 2 DECADE Il with dual ALEXYS 100 data system cellopton Fig 13 Typical configuration for parallel mode detection Two independent HPLC systems with dual channel support from OR 100 DECADE II and ALEXYS data system Fig 14 DECADE II with 2 columns and 2 VT 03 flow cells for parallel detection Navigation in dual cell menu All menus for a dual flow cell system are similar to a single cell system with 2 exceptions First in the top right corner a number is visible which indicates the active cell in d
41. mmended because of their high CO content The accuracy of certain pH electrodes is poor at high pH For applications at high pH it is sometimes better to calculate the pH from the OH concentration Organic modifiers acetonitrile strongly attenuate the signal of most carbohydrates in PAD and are therefore not recommended Some of these aspects will be discussed in detail CHAPTER7 Pulsed amperometric detection 57 Pulse settings In PAD of carbohydrates the working potential is applied as a series of 3 potentials During time interval t1 the detection potential is applied The data collection occurs within t1 during time interval ts sampling time The time difference t1 ts is the stabilisation time E V 0 8 one cycle 0 8 Fig 31 Potential steps in pulsed amperometric detection A part of t1 is used for detection ts The metal oxide layer that is formed during t2 is removed during t3 resulting in a renewal of the electrode surface During the next time interval t2 a monolayer of metal oxide is formed at the working electrode due to the high positive potential This monolayer is electrochemically removed from the electrode surface during time interval t3 by applying a negative potential Optimisation of wave forms LaCourse and Johnson 2 4 have published several papers on optimisation of wave forms in PAD Several considerations are important for the choice of the pulse duration Optimisation is depending o
42. n item can be 1 Control parameters with a cursor box O can be attained via cursor buttons and changed by the value button 2 Status without a cursor box a parameter reflects the current status 3 Functions parameters in CAPITALS are commands accessible via function buttons F1 F5 4 The Enter button is only used to accept changes in cell potential In the top right corner of each screen the name of the present screen is displayed If available the bottom left function button displays a previous screen and the bottom right one the next screen Fig 4 DECADE II keyboard The cursor is on Range which allows changes using the value buttons and The Enter button is only used to confirm changes in potential Ec 20 DECADE Il user manual ed 11 Overview of DECADE II screens Fig 5 DC mode CHAPTER 3 DECADE II controller Fig 6 PULSE mode 21 22 DECADE II user manual ed 11 Fig 7 SCAN mode n DECADE workstat SCAN 1 VFS present io masters yes ENSLAVE Fig 8 CONFIG screens CHAPTER3 DECADE II controller 23 Antec Leyden DECADE II CONFIG DC LC EC workstation PULSE SCAN Fig 9 DIAG screens Boot version Firmware version Checksum PREV Please stabilizing ce time remaini 24 DECADE II user manual ed 11 Parameters Explanation
43. n the working electrode material the sample constituents and the required detection frequency The impression may arise that the number of variables 3 potential steps and 4 time settings may lead to a time consuming optimisation procedure In practice the pulse mode is more straightforward The potential for the cleaning steps E2 and E3 are determined by the WE material At alkaline pH gold oxide is already formed at E2 gt 200 mV vs Ag AgCl At a higher potential the formation of a metal oxide layer is 58 DECADE II user manual ed 11 accelerated and a shorter time setting may be chosen In practise an E2 value of 750 mV during 200 ms t2 gives good results The choice of t3 is depending on the potential E3 and the t2 and E2 setting It is essential that the duration of t3 and the magnitude of E3 is such that a complete removal of the metal oxide is achieved Reductive dissolution already occurs at E3 lt 0 mV but a more negative voltage speeds up this process An E3 value of 800 mV during 200 ms Table VII or 300 mV during 360 ms 4 can be used The measuring potential is compound dependent usually literature data can be used as a Starting point for further optimisation A sampling time ts can be chosen between 20 and 100 ms in 20 ms steps These are multiples of the 50 Hz to prevent noise due to oscillations of the AC power supply Until a certain limit increasing ts will result in an increase of signal A limiting fact
44. nal processing has become an excellent alternative for hardware filters In its most simple form a running average filter takes the average of n data points to create a new data point For example in a 5 points running average filter output data point y 80 is calculated from measured data points x 80 x 84 as CHAPTER5 Noise suppression ADF 43 x 80 x 81 x 82 x 83 x 84 5 Each input data point has the same weighting factor of 1 5 In more advanced digital signal processing a more complicated equation is used to calculate the output data point y n vy 80 yin ajx n a x a 1 a x n 2 a x n 3 In contrast to the previous equation each data point has a different weighting factor a Sum of these weighting factors ao n will always be 1 Characteristic of noise filters is that processing the signal will result in a delay This is inevitable as the mathematics of digital signal processing requires a number of previous data points to process a new data point The filter characteristic in DSP is often named after the scientist who invented the mathematics behind the signal processing routine Well known names in this field are Bessel Chebychev Savitsky Golay Hamming and many others Amplitude response plot There are several ways to describe the filter characteristics An amplitude response plot gives important information on filter behaviour Suppose our signal of interest has a freque
45. ncy between 0 1 Hz and all higher frequencies are noise An ideal filter is shown in Fig 24 where signal frequencies between 0 1 Hz completely pass while frequencies of higher than 1 Hz are completely blocked Amplitude filter block 0 1 2 3 4 5 Frequency Hz Fig 24 Amplitude response plot of an ideal low pass filter with a cut off frequency of 1 Hz In practise filters behave a bit different from the ideal situation Amplitude response plot shows a more gradual attenuation profile at higher frequency 44 DECADE II user manual ed 11 This cut off frequency is where the output signal amplitude is 70 of the input signal also known as 3 dB point Amplitude 0 1 2 3 4 5 Frequency Hz Fig 25 An amplitude response plot of a low pass filter with a cut off frequency of 1 Hz It is a 2 A 4 B and 8 C pole Bessel filter In Fig 25 it is shown that the number of poles is important a filter behaves more ideal with increasing number of poles In a hardware filter the number of poles is the number of filter circuits that are placed in series 0 01pF stage 1 k 0 0990 k 0 040 stage 3 k 0 0834 k 1 023 Fig 26 Analogue 6 pole Bessel filter A digital filter does not have poles but it is characterised by the number of input data points used to calculate a new output data point For example a 9 point digital filter Savitzky Golay is given as Y 1 0 090909091 0 1688311
46. nt and contains timed events another file can be selected in the EVENTS SETUP screen If the file contains data that are no longer used the contents of the file can be erased Scroll to Time 0 00 min and press DEL Answer Yes to the question Delete timef ile YES NO 4 Programming the time file is done by entering all parameters for Time 0 00 and pressing ADD This is repeated for each time line in Table IV 50nA E c 002Hz Outep ADD ENDCYCL E 5 If atime already exists a message appears Overwrite time x xx Confirm this and continue programming by entering the new time with its corresponding settings Note that in the example at Time 14 96 min the offset is set to 00 to prepare for the next run An auto zero event is programmed 0 02 min later at Time 14 98 min 6 After entering all events press PREV or ENDCYCLE to enter the EndCycle screen Program the EndCycleTime This time is always 0 01 min higher than the last programmed events CHAPTER 6 Events and time files 51 EndCycleTime 7 To start the time file select RUN from the EVENTS SETUP screen The RUN screen appears and the system is waiting for a start command This can be a keyboard command or an external trigger line 13 from connector A on the rear panel 057V Ic 23 45n n A Offs 10 E c 0 80V 2Hz Cyc 1 28 3 096 waiting START AZERO 23 45nA 10 Ec 0 80V 0110 1 28 gt 30 C 212 33 TOP AZERO Output event
47. ntact 52 cleaning of detector 17 Common I O contact 52 53 compensation 36 cut off frequency 44 DC mode specifications 73 degassing mobile phase 15 digital filter 42 DSP 43 dual flow cell control 33 dual flow cell navigation 35 dummy cell external 81 internal 82 dummy cell test 81 E1 control 25 E2 control 25 electrochemical reaction 63 error messages 75 EVENTS example 49 filter 26 38 42 frequency 39 fuses replacement of 5 17 VE converter 33 VE relationship 63 I O contacts rear panel 77 specifications 52 86 DECADE Il user manual ed 11 Inject marker I O contact 53 inject marker trigger 51 installation DECADE II 13 integrator connection of trigger 51 pulse mode frequency 59 keyboard DECADE Il 19 maintenance cleaning of detector 17 detector 17 Mark I O contact 53 maximum compensation 36 messages 75 noise 15 16 56 58 68 73 79 noise filters 42 offset 37 output frequency 59 pulse mode 59 Overload I O contact 51 52 passivation with nitric acid 15 polarity 38 potential optimisation 63 pulse mode characteristics 56 literature references 62 optimisation 57 output frequency 59 potential settings 57 specifications 74 working electrode 60 pulsed amperometric detection 55 range 36 Relay 1 I O contact 52 Relay 2 I O contact 52 Reset I O contact 52 rotor Tefzel 56 rotor Vespel 56 RS232C 77 S N ratio 68 80 safety practices 5 Inde
48. off Off On autozero off Set Cancel Fig 10 DECADE II driver in ALEXYS data system Parameters in blue against white background are actual settings New parameters on the left side Method data can be set by clicking the Set button CHAPTER3 DECADE Il controller 31 A unique feature of ALEXYS data system is the scanning voltammetry module From the DECADE II device driver window all parameters are set The so called scan shell is opened and the scan is started 32 DECADE II user manual ed 11 CHAPTER 4 Detection and parameters 33 CHAPTER 4 Detection and parameters Introduction One of the characteristics of electrochemical detection is its tremendous dynamic range In amperometric detection peak heights may vary from micro amperes down to the pico ampere range The DECADE II covers such a wide range from 200 LA down to 10 pA full scale without being limited by electronic noise For this reason the DECADE Il is equipped with a 24 bit ADC and 20 bit DAC for analogue data output Internal organisation At the working electrode WE in the electrochemical flow cell the electron transfer takes place due to an oxidation or reduction reaction The resulting electrical current is amplified by the current potential I E converter Fig 11 Azero offset compensation Flow cell Output lesi E convertor 4 24 bits ADC fi CPU mm 20 bits DAC 1V or 10 V Full Sc
49. or is the accumulation of adsorbed species at the working electrode that attenuate the signal Another consideration not only for ts but for all time settings is that increasing the time will decrease the detection frequency Before sampling a stabilisation time is applied set by the duration of t1 In practice the stabilisation time determines the level of the background current When for example t1 100 ms and ts 100 ms there is no stabilisation of the current before sampling t1 ts 0 ms Depending on the potential setting of E2 and E3 a large positive or negative background current micro amperes may be detected which is seriously limiting the detection In practice often a 100 400 ms stabilisation time is used Teycle Fig 32 A magnified view of a chromatogram obtained with PAD The integrator frequency is 5 times higher than the detector output frequency resulting in a typical stepwise signal CHAPTER7 Pulsed amperometric detection 59 Output frequency An important difference between the DC and the pulse mode is the frequency of the output signal on the output In the DC mode the signal has a 10 Hz frequency in the pulse mode the frequency is determined by the duration of the pulse Once every cycle the ts signal is sent to the output This can be visualised by magnification of a peak in the chromatogram Fig 32 A stepwise pattern in the chromatogram is only seen on an analog chart recorder o
50. potential 63 Introduction 63 Electrochemical reactions 63 Hydrodynamic and scanning voltammogram 64 Optimisation using a voltammogram 65 Construction of a hydrodynamic voltammogram 68 Construction of a scanning voltammogram 68 Using scan mode in ALEXYS data system 70 Specifications DECADE II 73 General specifications 73 DC mode 73 PULSE mode 74 SCAN mode 74 Events 74 Rear panel I O connections 74 Physical specifications 74 Flow cells 74 Error messages 75 Rear panel 77 Connectors A B and C 77 10 DECADE II user manual ed 11 RS232C 77 Troubleshooting guide 79 No detector response 79 High cell current 79 Noisy baseline 79 Decreased sensitivity low S N ratio 80 Base line oscillations 80 Saturation of output 80 Dummy cell 81 External dummy cell 81 Internal dummy cell 82 Detector accessories 83 Index 84 Chapter 1 DECADE Il electrochemical detector 11 CHAPTER 1 DECADE Il electrochemical detector Congratulations on your purchase of the DECADE II This detector enables you to perform all applications using electrochemical detection The DECADE Il includes a highly stable Faraday shielded oven compartment accommodating column and flow cell This flow cell has surprised researchers for its unsurpassed S N ratio and therefore you now possess the best possible combination for extremely sensitive EC analyses The DECADE II covers the DC pulse and scan mode Important parameters in the DC and pulse mode can be chan
51. r on an integrator that has a higher sampling frequency than the output frequency of the detector In fact when this pattern is seen this means that the integrator has an unnecessarily high sampling frequency This leads to large data files but certainly not to a better chromatogram Peak width and integrator frequency There are two important considerations with respect to integrator frequencies applied in HPLC If the frequency is too low data will be lost and artefacts may be introduced If the frequency is too high large data files are generated which take up an unnecessary large amount of disk space As a rule of thumb the sampling frequency of the integrator is set such that a chromatographic peak is build up of at least 10 data points For a peak width of 10s this means that a sampling frequency of 1 Hz should be sufficient D E Fig 33 A detailed part of a chromatogram acquired at different integrator frequencies The integrator frequency is A 5x B 2 5x C 1 2x D 0 6x and E 0 3x the frequency of the pulse In case of PAD the duration of the pulse should also be taken in account When the frequency of the pulse is 2 Hz it makes no sense to acquire data on an integrator with a significantly higher frequency This would result in acquisition of multiple data points containing the same output value Fig 33A 60 DECADE II user manual ed 11 and B Matching the frequencies keeps the peak shape unchanged Fig 33C
52. rmware system Displays firmware version S Hold run scan Toggle holds or resumes execution of F resume stat time file or scan HOLD 0 1 run scan Holds or continues execution of time F stat file or scan Toggles between 1 and 0 Pressing hold again continues time file or scan were it has been hold Ic stat dc Displays the true non compensated S pulse scan cell current unaffected by auto zero or events offset setup run noise Id prog Board identifier for multi cell purpose C Indicates for which boards time file settings apply Binary coded INJ I L dc stat Displays or switches the position of the F S pulse stat injection valve toggles between inject I and load L If a manual injector with position sensor is applied it echoes the position of the injector If an CHAPTER3 DECADE II controller 27 Parameter screen Description Type electrically actuated injector is used optional it is possible to switch the injector with this function button KEYB test Enters KEYB screen for keyboard F test Press 2x F1 to leave MARK dc stat Triggers a marker signal on output F pulse stat MaxComp dc setup Maximum cell current that can be S pulse setup1 compensated for using auto zero Next several Enter next screen F screens NOISE test Enters NOISE screen for performance F test Offs dc setup dc Percentage offset can be set between C stat prog 50
53. rror Sensor board x error x board number Firmware program error Record error Incompatible FW version Incompatible FW Control board FW erase failed Sensor board x Upload checksum error Checksum error Temperature sensor 1 error Disconnect flow cell x Control board SRAM error Sensor board x SRAM error Please contact your local supplier if one of the above errors occur Furthermore the following messages can be displayed on the LCD screen during a measurement Table XI Messages Message Advice 01 Out of range Output is either above 1 0V or below 1 0V Pressing AZERO may give an adequate read out again If the message remains after pressing AZERO the autozero function is unable to compensate the background cell current Advice use a less sensitive range in the SETUP menu 02 PAD overload Charging current in pulse mode out of range Pressing AZERO may give an adequate read out again If not it is advisable to change the pulse settings increase t1 or use a less sensitive range 76 DECADE II user manual ed 11 CHAPTER 11 Rear panel 77 CHAPTER 11 Rear panel Connectors A B and C For detailed information on the I O contacts see page 52 Fig 44 DECADE II rear panel RS232C The RS232 interface provides full parametric control from a PC Programmable parameters comprise cell potential range auto zero offset filter electrical injector and control of DECADE II output contacts for control of
54. s Connector A and B on the rear panel enable control of or by external equipment Together with time files this supplies a powerful tool for development of automated methods Inject marker A manual valve with position sensor can be connected to C on the rear panel of the DECADE II which enables the inject marker on connector B The contact is high when the valve is in load position and low in the inject position It can be used to start the integration software when injection is done Overload Activated when a overload occurs see also page 75 for details 52 DECADE II user manual ed 11 Auto zero Enables external activation of the auto zero command This function is active only when the I cell is displayed To pos I L Forces the electrically actuated injector to position L load or inject Cell on off Switches on off the flow cell This input command can be used for example to switch on and stabilise the flow cell early in the morning by means of a timer Table V VO contacts connector A No Name YO Function 1 2 3 Relay 1 Out Contact between 1 common and 2 default or 3 Activated by time file Outp 0100 4 5 6 Relay 2 Out Contact between 4 common and 5 default or 6 Activated by time file Outp 1000 7 Cell on In Trigger to switch on cell 8 Reset In Resets a running time file 9 Overload Out Active when overload occurs out of range 10 AUX1 Out Free programmabl
55. s should be optimised Then the following steps are taken 1 A solution of the analyte at a concentration between 1 100 umol I is prepared in mobile phase 2 The electrochemical detector is stabilised in the DC mode at a high potential After stabilisation the background current is read from the display of the detector I cell and the noise is measured 3 The run is started by injecting the compound When at the high working potential no signal is obtained it may be concluded that the compound is not electrochemically active In such a case derivatisation of the compound may be an option 4 fa peak is measured the working potential is decreased by 50 or 100 mV and step 2 to 4 is repeated until the lowest potential setting Fig 40 5 The peak heights and the background currents are plotted against the working potential Fig 36 The working potential which gives the best sensitivity is obtained by plotting the signal to noise ratio against the working potential Construction of a scanning voltammogram The scan mode is programmed in the SCAN SETUP screen of the DECADE II Depending on the data acquisition software that is used and the experimental set up a full half or continuous scan cycle can be chosen Temp 30 C NEXT Fig 41 Programming the scan mode in the SCAN SETUP screen In the example of Fig 37 and Fig 42 a half scan is used sweeping the potential from 0 2 V to 1 2 V A full scan would inclu
56. sensitive Fig 39 For norepinephrine the VE curve is shifted to a lower potential at higher pH When the working potential is high E2 and the signal is diffusion limited an increase in pH will result only in a small increase of the peak height When the working potential is lower E1 and the signal is not diffusion limited the signal will strongly increase at higher pH In both cases the background current increases at a higher pH CHAPTER8 Optimisation of working potential 67 norepinephrine background 0 E 0 5 E EW 1 0 Fig 39 At a higher pH the IVE curve of norepinephrine is shifted to the left Reaction kinetics predict that electrochemical detection is mass flow dependent When the LC flow is stopped in LC EC the analyte will be oxidised completely and the signal decreases rapidly This means that the flow rate not only affects temporal peak width and analysis time but also peak height Also the background signal is sensitive towards fluctuations in the flow rate Therefore it is important to use a pulse free solvent delivery system nt LTL Fig 40 Construction of a hydrodynamic voltammogram for norepinephrine Chromatograms are obtained at cell potentials ranging from 1 0 V back to 0 4 V front with 100 mV steps 68 DECADE II user manual ed 11 Construction of a hydrodynamic voltammogram Before a hydrodynamic voltammogram can be obtained the chromatographic condition
57. ssage of air bubbles through the flow cell will lead to unacceptable noise levels and spikes Therefore the use of an in line degasser is strongly recommended In our experience a one time degassing step of the HPLC buffer is almost never sufficient If the DECADE Il is used for reductive ECD at a negative working potential additional steps should be taken to remove oxygen from the mobile phase These include degassing with Helium and the use of stainless steel tubing impermeable for oxygen Consult your flow cell manual for installation of the flow cell Connect the flow cell to the corresponding cell connector in the oven compartment All cell connectors are marked with a label for identification In case of a DECADE Il SCC connect the flow cell to the cell connector on the left side marked Cell 1 The cell connector inside the oven compartment is ESD sensitive Make sure that the flow cell is OFF when removing or connecting the cell cable Never switch ON the flow cell when the cell cable is not correctly connected the cell is only partly or not at all filled with buffer the outside of the flow cell is wet particularly the part between the auxiliary and working electrode connection because substantial damage to the working electrode or electronics may occur 10 13 Before switching ON the flow cell make sure that the buffer contains sufficient electrolyte buffer ions A stable baseline will never be
58. t is measured Optimisation of the working potential and the construction of a voltammogram is described Electrochemical reactions In electrochemical detection ECD a reaction of the analyte at an electrode surface is monitored This distinguishes ECD from most other detection techniques where detection is based on the physical properties of an analyte i e mass spectrometry molecular mass absorbance detection molar absorptivity For electrochemically active compounds the potential between reference electrode REF and working electrode WE determines the reactivity of the analyte at the WE The potential difference supplies the energy level needed to initiate or enhance the electrochemical reaction Different analytes may have different oxidation or reduction potentials which determines the selectivity of ECD OH OH Ho 2 CH CH NH On CH CH NH R 2H 2e for O Fig 35 Oxidation reduction reaction of norepinephrine An example of an electrochemical reaction is shown in Fig 35 norepinephrine is converted into a quinone by oxidation at the WE Two electrons are transferred at the WE resulting in an electrical current that is amplified by the controller 64 DECADE II user manual ed 11 Hydrodynamic and scanning voltammogram A hydrodynamic voltammogram is constructed when the pure analyte is not available and separation over an analytical column is required Furthermore under real chromatogr
59. timer in the NOISE screen and after 5 min stabilisation auto zero is activated and the dummy cell test is ready Noise of the internal dummy cell can be measured at the output As with the external dummy cell the noise should be better than 2 pA Detector settings in the NOISE screen are the same as in Table XII with exception of the oven temperature Temperature is switched off Please wait stabilizing cell current t ime remaining 05 00 CHAPTER 14 Detector accessories 83 CHAPTER 14 Detector accessories The electrochemical detector is shipped together with a number of parts The listing in Table below may not be complete see check list of delivery for complete listing Table XIII Accessories electrochemical detector Part number 250 0040 250 0107 250 0113 250 0122 250 0130 250 0128 250 0116 250 0118 250 0126 Component External dummy flow cell Column clamp 12 mm Fuse 2 5 AT 250 V RS232 cable External I O cable Output cable Mains cable Europe Mains cable USA Cell cable D connector For these and other DECADE II parts or flow cells contact your local supplier 84 DECADE II user manual ed 11 Index Index 85 ADF 39 Amplitude response 43 Auto zero I O contact 52 AUX1 I O contact 52 AUX2 I O contact 52 buttons DECADE II keyboard 19 capacitance WE 61 carbohydrates chromatogram 55 pulse settings 60 Cell off I O contact 52 Cell on off I O contact 52 cell on I O co
60. to devices that do not meet the relevant safety standards 54 DECADE II user manual ed 11 CHAPTER7 Pulsed amperometric detection 55 CHAPTER 7 Pulsed amperometric detection Introduction Several advanced features are implemented in the DECADE II One of these features is the so called pulse mode In pulsed amperometric detection PAD the working electrode WE is regenerated at a frequency of 0 5 3 Hz by the application of a series of potential changes This is particularly useful for certain applications where the working electrode is rapidly fouled due to adsorption of insoluble reaction products A well known application area of PAD is the analysis of carbohydrates Fig 30 1 t min Fig 30 Pulsed amperometric detection of 100 nmol l 2 pmol carbohydrates Peaks are sucrose 1 galactose 2 glucose 3 a lactose 4 and maltose 5 56 DECADE II user manual ed 11 Pulse vs DC The pulse mode is quite different from the DC mode 1 The output signal is sampled during a fraction of the total pulse cycle During the sampling time ts the signal generated at the WE is collected and this value is sent to the detector output This implies that the output is refreshed each pulse cycle In other words the frequency of data output is determined by the pulse duration When the frequency of the data acquisition system integrator is higher than the pulse
61. ttery inside Replacement of the battery should be performed by qualified service personnel Dispose the battery according to chemical waste only Replace blown fuses with fuses of proper type and rating as stipulated on the rear panel and specified in the installation section of this manual The fuse holder is integrated in the mains connector Ensure that the instrument is never put in operation with fuses of a different type This could cause fire V 100 240 V FUSE RATING WARNING RISK OF FIRE REPLACE FUSE AS MARKED 50 60 Hi Ad AVERTISSEMENT RISQUE DE FEU 260 VA 2 5AT 250V REMPLACEZ LE FUSIBLE COMME INDIQUE Do not use any organic solvents to clean the exterior of the detector Use a cloth wetted with water only to clean the detector Remove any dust on the protective screens that cover the fans in the oven compartment 18 DECADE II user manual ed 11 CHAPTER3 DECADE II controller 19 CHAPTER 3 DECADE Il controller Introduction The DECADE II has been designed for maximum functionality and ease of use The control of ECD parameters is such that without reading this chapter it should be possible to operate the detector This chapter is intended as a reference guide in case questions arise during operation The information shown in the numerous screens is presented in alphabetical order For each item an explanation is given together with the item s nature and the screen s of appearance The nature of a
62. ult of the noise measurement with the dummy cell is within specs the controller is excluded in a trouble shooting procedure R C WORK AUX REF RED BLUE BLACK The dummy consists of a resistor R of 300 MQ and a capacitor C of 0 47 uF in parallel The current is measured over the resistor according to Ohm s law V x R hence with a working potential of 800 mV the current drawn will be about 2 67 nA Slight differences as to this ideal value are due to the tolerance of the resistor 1 The capacitor functions as a noise generator and in fact resembles the capacitance of a well functioning VT 03 flow cell in an ideal HPLC set up The noise generated via the dummy should be less than 2 pA if the filter of the controller is set to off provided that the dummy is within the fully closed Faraday shield at the same position as the flow cell see Table XII for settings With a 1 second risetime the noise should be better than 1 pA Table XII Dummy cell test settings Parameter Setting Cell potential 800 mV Cell current 2 67 0 05 nA read out Oven 30 C stable Filter off or as specified Range 100 pA V The results of the dummy test must be comparable with the test sheet supplied with your controller If not please consult your supplier 82 DECADE II user manual ed 11 Internal dummy cell From the MAIN screen DIAG can be selected to enter the DIAG screen followed by selecting NOISE This activates a
63. um system Displays checksum S Comp de stat Toggles between ON and OFF C pulse stat releases auto zero offset Switches ON if AZERO is pressed Affects auto zero CHAPTER 3 DECADE II controller 25 Parameter screen Description Type compensation only not the offset CONFIG main Enters config screen F Contrast config Sets the contrast of display C Cyc run Displays the cycle counter If a time file S has to be executed more than once Cycles gt 1 this is the number of times a time file has been started see page 39 RESET external or QUIT sets Cy to 1 and returns to EVENTS SETUP screen Cyc scan setup Controls the nature of the cycle half C full and continuous Half means that the cell potential runs from E1 to E2 and stops at E2 Full means that the cell potential runs from E1 to E2 and back to E1 and then stops Cont means that the cell potential runs from E1 to E2 and back to E1 continuously MA Pressing STOP or finishing the cycle sets the potential to E1 Cycles events setup Controls the number of times a time C file has to be repeated This number can be 1 999 or continuous DEL prog Deletes the current data line from the F time file Deleting time 00 00 results in deleting the complete time file Confirmation is required DIAG main Enters Diag screen F DISPL test Enters DISP screen for display test F E1
64. versed Oxidative and reductive analyses generate opposite currents For data acquisition traditionally chromatographic peaks have a positive amplitude Therefore selection of polarity is useful Filter High frequency noise is efficiently removed and chromatographic peaks can be detected with better signal to noise ratio 315 0 313 0 n 16 0 lt x m O DN 311 0 11 0 2 00 4 00 6 00 0 00 2 00 4 00 6 0C Time min Time min Fig 17 Signal to noise ration is improved using a filter A vs B CHAPTER5 Noise suppression ADF 39 CHAPTER 5 Noise suppression ADF Introduction Besides for its tremendous linear dynamic range and selectivity electrochemical detection is well known for its very low limits of detection To further improve these detection limits the Antec Leyden engineers have developed ADF Advanced Digital Filter and the DECADE II has been equipped with it as a standard The improvement factor in signal to noise S N ratio depends on the frequency relation of signal and baseline noise S N improvements from a factor 5 up to more than 100 have been obtained To understand how a digital filter works first the importance of frequencies in chromatographic analysis will be explained Then we will look at peak width filter settings cut off frequency amplitude response plots and finally at a few chromatograms before and aft
65. x scan mode example 68 scanning voltammogram 64 specifications 74 service 6 spare paris 6 specifications DECADE Il 73 Start I O contact 52 Status I O contact 53 Status L I O contact 53 t1 control 28 Tefzel rotor 56 timefile 49 example 49 To I I O contact 53 To L I O contact 53 to pos L I O contact 52 troubleshooting 79 ts 56 valve installation 14 Vespel rotor 56 voltammogram construction 64 68 introduction 63 working electrode material 60 87

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